Line-switch system



W. T. POWELL.

LINE SWITCH SYSTEM. APPLICATION FILED MAYM, 1919.

Patented 11116 21, 1921.

INVENTOR WINFRED T. POWELL ATTORNEY UNITED STATES PATENT OFFICE.

WINFRED T. POWELL, OF ROCHESTER, YORK, ASSIGNOR TO THE STROMBERG- CARLSON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK,

A CORPORATION OF NEW YORK.

LINE-SWITCH SYSTEM.

Patented June 21, 1921.

Application filed May 14, 1919. Serial No. 297,086.

To (ZZZ whom it may concern:

Be it known that I, WINFRED T. POWELL, a citizen of the United States, residing at l? chester, in the county of Monroe and Fitate of New York, have invented certain new and useful Improvements in Line Switch Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone sys tems, and more )articularly to telephone systems employing automatic switches for completing connections between calling and called subscribers.

The present invention has for its purpose the improvement in the operating cirmiits of distributor switches of the type which have no'norinal or home position; that is, the distributor switch not restored to normal position or disconnection, but remains in engagement with the trunk or line last used.

One feature of the invention relates to the arrangement whereby the line switch associated with the called line is prevented from seizing the trunk with which it happens to be in engagement when its associated line is called. Other features not specifically enumerated will appear from the detailed description and claims.

The figure of the drawing diagrammatically represents a portion of a telephone system in which the portion of the drawing appearing at the left of the dotted line represents a. calling substation and line, together with the openting circuits of a line of distrilmter switch. The portion of the drawing included between the two dotted lines diagrammatically represents the operating circuits of a connector switch, while that portion of the drawing appearing at the right of the dotted line representsthe operating circuits of the distributer or line switch individual to the called line and also shows the called substation circuits.

The line or distributing switch which will be referred to in the detailed description, wnnprises a ii at rotary switch in which there are four series of contacts arranged to form an arruate bank. Four brushes are pro- .vidmil each one of these brushes cooperating with one of the four series of contacts. These brushes are rotated by a stepping magnet but are not restored to normal or disconnection, since they remain in engagement with the trunk last used until the line with which they are associated becomes engaged as a called line. At that time the brushes of the switch are moved out of engagement with its fixed contacts or terminals, into a position between these contacts. This is accomplished as follows: The brushes of the switch which are designated 2, 6, 11

and 12, are fixed to a rotatable shaft which is provided with a ratchet wheel 32, arranged to be driven in one direction only. lhis rachet wheel is engaged by two pawls 33 and 34L, carried by the armature of the motor magnetMM. The brushes of the line switch are so arranged with respect to the line contacts or terminals, that when the motor magnet MM is energized and deenergized, the paws 33 and 3e will move the switch brushes from one set of contacts to the next set of contacts in the series. It will thus be seen that when the motor magnet Mlli is energized, the line switch brushes will. be advanced to a position intermediate 02": the sets of contacts.

The connector switch which will be referred'to in the description may be of the type substantially the same as that shown in the patent to Keith et al., 815,176, issued Mar. 13th, 1906.

It is believed that the invention will best be understood by describing the operation of establishing a connection from the calling substation at A, to the called subscribers station at B. When the calling subscribed at A. removes his receiver from its switchhook, the line relay LR is energized over a circuit extending from grounded bat tery, winding of this relay, inner back contact and armature of cut-off relay CO, through the calling subscribers line and sub-station circuits, upper armature and back contact of the cut-off relay, to ground. At its left hand armature and contact spring, a: guarding potential is applied to the test contacts of the calling line appearingat various connectors. The circuit for applying this guarding potential is traced from ground, through the line switch brush 2, left hand spring and armature of the line relay, conductor 8 to the multiple test terminals of the calling line at various connectors. At the right hand armature and front contact of the line relay an operating circuit for the motor magnet MM is com- Jarmatures.

I pleted from grounded battery, winding of this magnet, through its self-interrupting contact sprin s l, conductor 8, lower back contact and armature of the cutoli' relay Cl), right hand armature and front contact of the line relay,'through the test brush 6 of the line switch and over the test conduc tor of busy trunks to ground at the left hand front contact and armature of the slow releasing relay 7 at various busy connector switches. v

The motor magnet MM continues to ad Vance the line switch over circuits similar to. that just described until an idle trunk is reached where an idle condition indicated by'reduced potential on its test terminal. As soon asthe idle trunk is seized, cut-oil relay-CO is operated over a circuit completed from grounded battery, winding of motor magnet MM, conductor 8, winding or the cut-ell relay, left hand contact spring and armature oi the line relay LR to ground over line brush 2. Prior to this time the cut-off relay had been short-circuited by path traced from grounded battery, winding of the motor magnet MM, self-interrupting springs l, conductor 5, lower back contact and armature of the cut-oil relay, right hand armature and front contact of the line relay LR, to ground over test brush (5, and the test terminals of busy trunks. The cutoll relay GO, upon energization attracts its armatures, and at its upper armatures tends the conductors of the calling line to the conductors of the selected trunk, and also interrupts the energizing circuit of the line relay LR, causing this relay to retract its At the lower armature and front contact of the cutoff relay, this relay completes a locking circuit for itself from ground applied to conductor 9, either at the left hand armature and front contact of the slow releasing relay 7, or at contact 10 of the oil normal switch at the connector, line switch test brush 6, lower front contact and armature of the cut-oil relay, back contact and spring of the line relay Lit, winding of the cut-oil relay CU, conductor 8, winding of the motor magnet MM, to grounded. battery. The apparatus is now in condition to receive the impulses from the calling subscribers dial switch. The motor magnet, such as MM of the line switch is so designed that it will not operate in series with the cut-ofi relay, such as CO, but when the motor magnet is once energized it will remain operated in series with'the cut-oil relay.

In this disclosure it is not deemed necessary to disclose the operating circuits of the selector switch, although it will be readily understood how the line switch circuits of this invention will cooperate with such selector switch circuits. Inasmuch as the only numerical switch disclosed, is a connector, it will be necessary for the calling subscriber to transmit only two series of impulses, one corresponding to the tens digit, and the other to the units digit of the wanted number. As soon as the calling line was extended to an idle connector, the stepping relay of that connector, is energized over a circuit completed from grounded battery, winding of this relay, line switch brush l1, inner front contact and a mature of the cut-off relay CO, through the calling subscribers line and sub station circuits, upper armature and front contact of the cut-oil relay, line switch brush 12, winding of the impedance coil to ground. On the first energization of the stepping relay SR, the slow releasing relay is energized. In response to the tens series of impulses, the stepping relay SR vibrates its armature, but since the relay T is slow to release, it will not he deenergized during momentary interruptions of its energizing circuit.

On each retractionoi' the armature of the stepping relay Sit, an energizing circuit. is completed for the primary motor magnet PM, which moves the connector switch through its primary or groups selecting movement. This energizing circuit is traced from grounded battery, winding of the primary motor magnet PM, side switch wiper 14 in its first position, slow releasing relay 15, right hand front contact and armature of the slow releasingrelay 7, back contact and armature of the stepping relay SR,

b0 g1 ound.

On the first completion of this circuit, the slow releasing relay 15 is energized and does not deenergize until the close of the series of impulses. l Vhen the relay l5 attracts its armature, an operating circuit for the es cape magnet TSC is closer. from grounded battery, resistance, winding of the escape magnet, the spring and armature ot' the relay 15, to ground. At the close of the tens series of impulses, the stepping relay SR attracts its armature a relatively long in terval, so that the slow releasing relay l5 deencrgizeslo interrupt the operating circuit of the e cape magnet. This magnet, as well known, operates on deencrgization to move the side switch'wipers into a succeed.- ing position, in this instance its second position.

lVhen now the subscriber transmit-s impulses eorresoondingto the units digit of the wanted nuri1ber,the stepping relay SR will again vibrate its armature, but in this instance will complete a'n operating circuit for the secondary motor magnet SM, from grounded battery, winding of this magnet, lower armature and back contact of the test relay 16, side switch wiper let in its second position, slow releasing relay 15, right hand, front contact and armature oi the relay 7, heel: contact and armature or" the relay SE, to ground. The magnet SM and the relay to are energized in. this circuit, the relay 15 operating to complete the energizing circuit :tor the escape magnet as previously described. The motor magnet SM operates as is well known to advance the connector switch in a secondary direction to select the wanted line from the previously selected group of lines.

At the close of the units series of impulses, the connector switch is in operative relation to the connector terminals of the wanted subscribers line, so that if the Wanted line is idle the connection may proceed, as follows: Since there is no guarding potential on the test terminals 17 of the wanted line, the escape magnet ESQ will be de'elnergized at the close of the units series of impulses and will now move the side switch wipers such as 1%, 22, 25, 26 and 27 into their third, or ringing position. In this position the called subscriber is signaled by ringing current supplied over a circuit from grounded batcry, ringing generator 18, interrupter 19, lamp 20, ringing trip relay 21, side switch wiper in its third. position, connector brush 23, through the bell at the called subscribers substation, back to connector brush 2 1, side switch wiper 25, to ground. In the third position or" the side switch wipers, a circuit is also completed for the escape magnet from grounded battery, resistance, winding of this magnet, side switch wiper 26, back contact and'arinature of'the release magnet REL, to ground. The escape magnet remains energized until the called subscriber responds by removing his receiver from its switchhook, whereupon the marginal trip relay 21 receives sufficient current to attract its armature. The escape magnet is then short-circuited at the front contact and armature of the trip relay 21, and the side switch wipers are moved into their fourth, or talking position. In this position of the side switch wipers, a telephonic circuit is completed; the talking battery for the callinn subscriber being supplied through the winding; of the stepping magnet SR and imp-edance coil 13, while the talking battery for the called subscriber is supplied through the winding of the impedance coil 14. A guarding potential for the called line is supplied tl rough the side switch wiper 27 in its third or fourth positions.

It the called line had been busy at the close of the units series of impulses when the connector switch brushes were placed in eng..gement with this line, the escape magnet would have been held energized over a circuit traced from grounded battery, resistance, winding of the escape magnet, makebclore-break contact and spring at relay 15, winding of the test relay l6, spring and contact 29 at this relay, side switch wiper 27 in its se ond position, test brush 30, test terminal 17, to ground at side switch wipers 27 at another conne tor switch. The test relay 16 is energized in this circuit and attracts its armature to complete a locking circuit for itself, from spring and inner armature of the test relay, contact 80, and oil normal spring, to ground. At the upper armature of the test relay, a circuit is closed for applying a busy tone from the busy machine BZ to the calling subscriber.

W hen the calling subscriber desires to disestablish the connection, either because the wanted line is busy or because the conversation is completed, he replaces his receiver on its switchhook. This causes the stepping relay Sit to deenergize, and after a short interval 0r time, the slow release relay 7 also deenergizes. A. circuit is thereupon completed for the release magnet from grounded battery, winding of the release magnet REL,

off normal spring and contact 31, right hand back contacts and armatures of the relays 7 and SE, to ground. l/Vhcn the slow releasing relay 7 retracted its armatur-es, the holding ground for the cut-oil relay CU was removed, and the cut-oif relay decnergized to reconnect the line relay LR to the calling subscribers line. Since the line switch has no normal position, these brushes remain in engagement with the contacts or terminals of the trunk last used.

It has been found that when line switches of this'character have been employed, that means must be provided to prevent the line switch associated with the called line from selecting a trunk whenever the called line is seized. In accordance with the present invention whenever a line is selected as a called line, such as B, the motor magnet MM is energized over a circuit extending from grounded battery, and back contact and armature of the motor magnet M'M' and later the resistance extending around this contact and armature, lower armature and back contact of the cut-off relay Ctl, continuity contacts of the line relay LR, test terminal 17 test brush 30, side switch wiper 27 in its third or fourth positions, to ground. Subsequently the motor magnet MM and cut-off relay CO are energized in series over conductor 34 and test terminal 17. The motor magnet MM is thus held energized during the conversation, and thereby holds the brushes of its associated line switch out of engagement with its trunk terminals, so that a trunk will not be seized by this switch at this time. When the called line is no longer busy its cut-off relay and motor magnet deenergize and the magnet advances the associatec finder brushes into engagement with some trunk terminals.

It will be noted that when a line is seized by a connector switch, the ground on the test wire operates the stepping magnet of the called line switch to move and hold the brushes or wipers of this switch between the contacts or terminals of its contact bank.

with the ,contacts of the contact ban ,CO, but this cut-oil relay is she After the brushes or wipers of the line switch have moved away from engagement it it is then necessary to operate the cutby the contacts of the stepping magnet when the contacts of the motor magnet MM are closed. ll hen the contacts of the ste, ping magnet are open, the cut-ofi relay CQ is in series with thestepping magnet and without the resistance across the contacts of the stepping magnet, the sudden rush of current through the cut-oil relay in series with the stepping or motor magnet would cause a surge of current in the stepping i. in the opposite direction from the current which originally operated it, with the result that the stopping magnet might release. However, with the res. .ince coil about i, contacts of the stepping magnet placed in parallel with the cut-oil relay until this relay operates, the mentioned of our is shunted through tie resi. thus does not affect the stepph l Vhile the circuits of the present invention have been employed in connection with a line switch, it will be understood that they may be used equally well in op :at

dis tributer switch, such as is employed in apportioning calls to operators in call distributing systems. In the present disclosure only line and connector sw tch circuits are shown, but it will be readily understood that it the present invention is enu loyed in a larger system, that the line switch cisc s willcoiiperate with sole tor switches as well. as with connector switch circuits.

What I claim is :7

1. In a telephone system, telephone lines, connector switches having coi'itoctsin which said lines terminate, a line swi ch A} l with fixed and movable contacts ha i I no normal position, each of the said telephone lines terminating in the movable contacts of one of said line switches, means 1 connecting with any line through one oi the said connector switches, and n'ioans ol'leet vo thereupon for moving said moval'ile contacts of the associated line switch out 0:? gagement with its fixed contacts.

2 In a telephone system, telephone lines, connector switches having contacts in which said lines terminate, a line'switch provided with fixed and movable contacts h ving no normal position, each the said t ephone lines terminating in the movable contacts oi"? one of said line switches, i'i'ieanr for connecting with any line through one oi the said connector switches, and means ellective thereupon for moving said movable contacts of the associated lineswitch out of engagement with its fixed contacts to a position intermediateof said contacts.

3. In a telephone'system, a plurality of telephone lines, a connector switch in which some one of v.

the said lines terminat a line switch in dividual to each line having no normal position, outgoing lines tern ating in eachline switch, means for causing. to seize one or said telephone, lines, and means then effective for causing the line switch individual to the selected telephone line to move out of engagement vith all of said outgoing lines.

d. In a telephone system, a telephone line, means for seizing said line as a called line, a line switch individual to said line, outgoing lines at said switch v-rith some one of which said line switch. is normally in engagement, and means operative when, the telephone line is seized as a called line to move said line switch out of eng gement with said outgo ing lines. 1

ln a telephone system, a telephone line arranged to function as a calling and a called line, a lineswitch individuz'il to said line, outgoing lines at the said switch with some line of which saidswitch is normally in engagement, operating means for said switch having two circuits, one for advanc ing the switch to select an idle outgoingline,

and the other to move said switch out of engagement'with any of said outgoing lines, when the telephone llnc 1s seized as a called line. r

6. In a telephone system, a telephone line, means for sizing said line as a called line, a line switch i dividual to said line, outgoing lines ninating at said switch with .llC-ll said line switch is normally in engagement, and a motor magnet for adv-an i g said switch, saidmotor maghavin two circuits, one for advancing V ch to select an idle outgoing line, and th other to move said switch out ofen- ,oment with any of said outgoing lines.

In a telephone system, a telephone line, means for seizing said line as a called line, a line switch individual to said line, outlines at said switch with some one of wl h said line switch is normally in en- ;ent, a cut-oil relay and a motor magassociated with said line switch, and a uit includ ng said motor magnet and cutoil relay having two branches, one completed whenthe lineis calling, and the other branch completed when the line is seized as a called line.

8. lin a telephone system, a telephone line, means for seizing said line as a called line, a line switch. individual to said line, outgoing lines at said switch with some one of which said line switch is normally in engagement, a cut-off relay and a motor magnet associated with said line switch, and a circuit including said motor magnet and cutol relay having two branches, one completed w ion the line is calling, and the other branch completed when the line is seized as a called line, said motor magnet being energized a connector switch when one branch of the circuit is completed and deenergized when the other branch is completed.

9. In a telephone system, a plurality of telephone lines, a line switch individual to each line, trunk lines terminating in said switch, a motor magnet operating on energization and deenergization to cause said switch to more from one trunk line to the next succeeding trunk line, mechanism for seizing any one of said lines as a called line, and means operative thereupon for maintaining energized the motor magnet of the line switch associated with the selected line.

10. In. a telephone system, a plurality of telephone lines, a line switch individual to each line, trunk lines terminating in said switch, a motor magnet operating on energization to move said switch between two adjacent trunks on each energization and on deenergization into engagement with the next succeeding trunk, mechanism for seizing one of said lines as a called line, and means operative thereupon for maintaining energized the motor magnet of the line switch associated with the called line.

11. In a telephone system, a plurality of telephone lines, a line switch individual to each line, trunk lines terminating in each of said line switches, a motor magnet operating on energization to move said switch out of engagement with any of said trunks and operating on deenergization to cause said switch to engage one of said trunks, means for seizing any of said lines as a called line, and means operative thereupon for maintaining energized the cut-off relay and motor magnet associated with the called line.

12. In a telephone system, a plurality of lines, an individual line switch for each line, provided with brushes and with fixed contacts, outgoing circuits multiply connected to said fixed contacts, means for normally maintaining said line switches in engagement w'th the contacts of some outgoing circuits and means for moving a line switch from a set of lined contacts as soon as the line of said last mentioned line switch is seized as a called line.

13 in a telephone system, a plurality of telephone lines, an individual line switch for each line, outgoing circuits multiply c0nnected to said line switches, means for maintaining each line switch in an engagement with some outgoing circuit and means for moving the line switch or" a called line from the outgoing circuit with which said last mentioned switch is in engagement when said called line is seized.

1%. lln a telephone system, a plurality of telephone lines, a line switch for each line provided with line contacts and trunk contacts, trunk circuits multiply connected to said trunk contacts, means for maintaining said line contacts in engagement with some one of said trunk contacts and 'means for moving the line contacts of a called line switch from the trunk contacts with which it is in engagement.

In witness whereof, I hereunto subscribe my name this 13th day of May, A. D. 1919.

WINFRED T. POWELL 

